Heater



July 2, 1946.

H. J. DE N. MCCOLLUM HEATER Filed Sept. 5, 1942 3 Sheets-Sheet l jznapemmc ozzum July 2, 1946.

H. J. DE N. MCCOLLUM 2,402,970

HEATER Filed sew, 5, 1942 s Sheets-$heet 2 J l 2, 1946. H, J. DE' N.MCCQ LU 2,402,970

HEATER s sheets-sheets Filed Sept. 5., 1942 Patented July 2, 1946 HEATERHenry J. De N. McCollum, Chicago, 111.; Theima.

McCollum executrix of said Henry-J. De N.

McCollum, deceased Application September 5, 1942, Serial No. 457,447

4 Claims. 1

My invention relates to heaters and more particularly to heaters 01 theinternal combustion type, although it is not necessarily limited to thistype of heater.

In heaters'of the internal combustion type, it is common to providefinned heat transfer means for transferring heat from the products ofcombustion to the ventilating air directed over the heat transfer meansby a blower or other means for circulating air.. The heated products ofcom:

bustion are ordinarily directed against the fins at one end of the heattransfer means and where the hot products of combustion first come incontact with the fins, these fins are raised to a I temperature which ismuch in excess of the temperature of other portions of the fins andparticularly that portion adjacent the outlet end of the heater. Thereis a practical limit to the temperature to which the fins can be heatedand this limits the total quantity of heat which can be given off by aheater of any given size and shape.

An-object of my invention is to provide a heater wherein the heattransfer means is heated to a substantially uniform temperaturethroughout its length and thereby provide a more eificient heater havinga higher heat output for a given size.

Another object of my invention is to provide a heater wherein thetemperature range between difierent parts of the heater is reduced to aminimum and stresses and strains caused by great variations intemperature of the different parts are avoided. Another object of myinvention is to provide an extremely light and compact heater having'ahigh heat output and particularly adapted forv use in aircraft.

Another object of imr invention is to provide a heater wherein the partsare so designed, as to have a. m \tlmum strength for a minimum weightand wherein these parts may be made as strong as desired to heat therequirements of any given type of service.

Another object. of my invention is to provide a new and improved heaterwhich can be economically manufactured by conventional equipment andusing conventional methods.

Another object of my invention is to provide a new and improved heaterhaving more efficient means for transferring heat from the gases ofcombustion to a' heat exchanger and from this heat exchanger toventilating air.

Another object of my invention is to provide anew and improved heaterwhich more efficiently transfers heat from a gas-to a metal surface.

Another object of my invention is to provide a new and improved. heaterwhich more efiiciently transfers heat from a metal surface to a gas.

Other objects and advantages Will become apparent as the descriptionproceeds.

In the drawings:

Fig. 1 is a side elevational view of 'a preferred embodiment of myinvention. In this view, part of'the casing for the ventilating air isbroken away.

Fi 2 is an enlarged end view looking in the direction of the arrow 2 inFig. -1. In Fig. 2, the inlet part or the casing for the ventilating airhas been omitted to show more clearly the arrangement of -the externalfins for heating this air.

- Fig. 3 is an enlarged longitudinal, sectional view on an enlargedscale and is taken on the line 5-5 of Fig. 3. The drawings disclose anembodiment of myinvention wherein the body In of the heater is enclosedin a casing H for directing ventilating air thereover. The body Incomprises a pair of conical'castings l4 and I6 of aluminum or othersuitable material. The castings l4 and I6 have telescopic .ends l8 and20, respectively, and in telescoping these ends the casting l6 and itsend 20 are heated and slipped over the cold casting M to form a shrinkfit which firmly attaches the casting Hi to the casting to form aunitary structure. 7 r The casting M has an annular wall 22 integralwith and located between a radially projecting series of interior fins24 and a series of radially directed exterior fins 26. The forward endof the wall 22 is constructed and arranged to provide a rectangularrecess or combustion chamber 28 and terminates in a threaded boss 30.

The casting l6 has an annular wall 32 integral .with and located betweena series of radially diair. This ventilating air is supplied to theinlet end 40 of the casing by a ram, blower, or any g I 3 other suitablemeans and is discharged through the outlet 42, which may communicatedirectly with the airplane cabin or other space to be I heated or may beconnected to a system of ventilating ducts for directing the heated airin any desired manner. In lieu of providing a blower or ram for forcingventilating air into the inlet end 48 of the casing, a suction blowermay be provided for the outlet 42 to create flow of ventilating airthrough the casing l2.

A part of the air flow in the inlet 48 enters a I ,Venturi-tube 44,which is screwed into a bushing 46 in the boss 38 of casting I4. TheVenturitube 44 has a restricted throat 48 to which fuel issuppliedthrough openings 58 in a-fuel supply pipe 52, which may be connectedeither to any suitable fuel tank or to a source for supplying an undulyrich mixture of fuel and air. The raw fuel or rich mixture of fuel andair supplied by the pipe 52 mixes with air flowing through Venturi-tube44 and forms a combustible mixture which is delivered with a whirlingmotion to the combustion chamber 28 through openings 54 in a burner tube56.

The combustible mixture'supplied to the combustion chamber 38 is ignitedby electrical igniters 58 which are supplied with current from anysuitable source. In the drawings, I have illustrated a-heater havingthree igniters 58 closely grouped, but my heater is not limited to thisnumber and arrangement and any other desired number and arrangement ofthese igniters may .be utilized. The hot wires 68 of these ignlters arein communication with the combustion chamber 28 through openings 82which are protected from 3 cut out.

A mullier 68 is confined between the internal of-these fins andcooperates therewith to form passages ll through which the burned gasesflow A tubular abutment 86 is screwed into the threads 81 at the outletend of wall 32 and has a tapered portion 88 formingaan abutment for theflared end 88 of the exhaust pipe 14. A sleeve 92 surrounds the pipe 14and has a tapered end 94 which engages the flared end 98 of the exhaustpipe and clamps it against the abutment 88 under the force exerted by atubular nut 95. The

lefthand end of the sleeve 82 is inclined, as indicated at 88, as I havefound that this inclination reduces the tendency of the exhaust pipe 14to break oil? adjacent the endof the sleeve 92 under continuedvibration.

' In the operation of my'invention, a portion of '52 to form acombustible mixture which is delivered to the combustion chamber 28 witha whirling motion through openings 54 in burner tube 56. Thiscombustible mixture is ignited by the igniters 58. The heat therebycreated in the combustion chamber 28 is partially absorbed by the wallsof this combustion chamber and transmitted to the adjacent portions ofthe fins l4.

bustion chamber 28 to the outwardly flaring portions of the passages Hlocated between the internal fins 24. The gases leaving the combustionchamber 28 are at a maximum temperature and tions of the fins 24 and thewall 22.

The rate of heat transfer from the ga to a metal surface varies greatlywith the direction at which the gas strikes the metal surface and ishighest when the gas scours the surface by being projected substantiallyvertically against this surface. The hot gases of combustion are notdirected against the outwardly flaring wall 22 and i fact tend to hugthe adjacent wall of the muiller shell so that relatively little heat istransfin 24 and 34 of the two castings and has a sheet metal shell 18which abuts the inner'edge's i from the combustion chamber 28 to theexhaust pipe 14. The interior of the shell 18 is filled with glass woolor stainless steel wool, orother suitable heat resisting and soundabsorbing material and elongated slots 12 in the shell 18 provideacousti-couplings between the passages 1| and the interior of themuiller.

That end of the muiiler shell which is adjacent the combustion chamber28 is rounded as indicated at [3 and serves to direct the burned gasesinto the passages H with a minimum of resistance to the flow of thesegases. This end of the muiller-is provided with an airspace 16 whichprotects the glass wool against the intense heat occasioned by thecombustion chamber 28. Opening's I8 in a partition 88 formacousti-couplings between the space 18 and the portion of the mufflershell in which the glass wool is located. The

other end of the muiller shell-is illustrated as being provided with arounded cap 82, which forms an air space to the left of the partition 84defining the lefthand end of the compartment containing the glass'wool.

. gases flow through the passages H, they give'up ferred directly fromthe gases to the outwardly flaring portion of the wall 22 and most ofthe heat received by this wall is conducted to it by the adjacentportions of the internal fins 24.

On the other hand, the ventilating air is directed against the outwardlyflaring wall 22 and scours this wall to remove great quantities of heat,therefrom. In other words, the heat transfer directly betwee the hotgases of combustion relatively inefficient, whereas the heat transferfromthe outwardly flaring portion of this wall to the ventilating air ishighly efficient, with the result that this outwardly flaring v portionofthe a wall 22 and the adjacent portions of the internal fins 34 andexterior fins 28 are maintained at substantially the same temperature asother portions of this wall and these fins at the same tem- .perature asthe corresponding wall and fins of the other casting.

The products of combustion pass from the outwardly flaring portions ofthe passages II to the straight or cylindrical portions of thesepassages and then to the entrained portions of these passages leading tothe exhaust pipe 14. As these their heat to the interior fins and tocasting walls and when these gases reach the inwardly directed portionsof thepassages l these gases are allproachlng their minimum temperature.The heat transfer between these gases and the inwardly directed portionof the casting-wall 82, however, is a'maximum, since the gases ofcombustion are directed against and tend to scour this entrained portionof the wall. At the same the air flowing in the inlet 48 entersVenturi-tube. 44 and mixes with fuel supplied through pipe The hot gasesof combustion flow from the com- I give up part of their heat to theadjacent por-- and the outwardly flaring portion of=wall 22 is time theheat removed from this entrained portion of the wall 32 by theventilating air is a minimum and the resulting balance maintains theconical portion of casting 32 at substantially the same temperature asthe conical portion of casting l4 and the connected cylindrical portionsof both of these castings. In other words, my novel structure provides aheater wherein the heat transfer means is maintained at substantiallyuniform temperature throughoutits entire length and an extremelylightweight, compact and efficient heater can be provided by designingthe heater so that all parts of the heat transfer mean operate atmaximum temperature.

The heated ventilating air flowing through the casing outlet 42 may bedischarged directly into the airplane cabin or other space to be heated,or may flow through a suitable duct arrangement for dividing up thisheated air and delivering it to specific locations. The cooled gases ofcombustio are discharged to atmosphere through the exhaust pipe 14.

The muiller I0 absorbs sounds entrained in the ases of combustion. Thismuiiler also cooperates with the walls 22 and 32 to direct the flow ofthe gases of combustion and directs the relatively cool gases ofcombustion against the conical portion of wall 32 while permitting theextremely hot ases of combustion to flow along the conical portion ofwall 22 in such a way as to give up relativel little heat to this wall.

In the embodiment of my invention'shown in the drawings, the severaligniters 58 are provided with individual housings I00 which are attachedto the casing I2 and have open lower ends communicating with openingsI02 formed in this casing. The housings I00 have openings Hit throughwhich the igniter wires I06 extend and while a small amount ofventilating air may escape through these openings I04, the provision ofthe housing I00 forms a convenient means for preventing the igniters 58from reaching unduly high temperatures and at-the same time preventingthe escape of large quantities of air from the casing l2 around theseigniters.

My novel, double cone heat exchanger is not limited to use in 'a heaterhaving a combustion chamber therein. This double-cone or opposedalignment therewith, inner and outer wall means forming a flow passagefor conducting the hot products of combustion from saidcombustionchamber to said exhaust passage, said flow passage being ofannular cross section, the inner and outer walls of said passageadjacent the combustion chamber flaring outwardly at an abrupt angle tothe axis of said chamber, and said walls of said flowpassaige adjacentthe exhaust end of the heater converging toward the axis of the exhaustpassage at an abrupt angle to said axis, a. jacket spaced at anapproximately uniform distance from the outer wall of said flow passagethroughout its length, forming a passage for ventilating air betweensaid outer Wall and said jacket, said air passage being of annular crosssection with its 'walls flaring outwardly from the end adjacent thecombustion chamber and con verging at the other end adjacent the exhaustpassage so that the air passage substantially follows the contour of theflow passage, and means delivering ventilating air so as to flow throughsaid passage in the same. direction as the combusbustion gases impingeforcibly against the con verging surface of said wall adjacent theexhaust cone type of heat exchanger may also be utilized in a heaterwhich is supplied with exhaust gases from an internal combustion engineor which is supplied with heated fluid from any other suitable source.

While I have illustrated and described only a single embodiment of myinvention, .it is to be understood that my invention is not limited tothe details shown and described, but may assume numerous other forms. Myinvention is. to be construed as including all modifications andvariations coming within the scope of the appended claims. i

I claim: 4

1. In a heater of the class described, wall means forming a cylindricalcombustion chamber and a tubular exhaust passage in substantially axialend of the heater.

2. In a heater as defined in claim 1, said outer wallof the flow passagefor combustion gases being of relatively thin metal and having integralfins circumferentially spaced, extending substantiallythroughout thelength of the passage and projecting radially inward and substantiallyacross it, subdividing said passage into a'plurality of longitudinalchannels to which the flow of hot gases is confined, said wall havingalso a. series of outwardly projecting radial fins extendingsubstantially throughout the length of the ventilating air passage andsubstantially across it to the said jacket, subdividing said passageinto a plurality of longitudinal channels confining streams ofventilating air and transferring thereto the heat absorbed by said walland its inwardly projecting fins.

3. Ina heater as defined in claim 1, the inner wall of said fiow passageor the combustion gases comprising a hollow metallic shell filled withsound absorbent material and having $112.11 perforations distributedover its lateral area.

4. In a. heater as defined in claim 1, the walls of said flow passagefor the products of combustion intermediate said outwardlyflaring-portions and said converging portions being substantiallyparallel to the common axis of the combustion chamber and exhaustpassage, whereby said produots of combustion experience an abrupt changeof direction in passing from the outwardly flaring portion of the flowpassage into said intermediate portion and impinge forcibly against the

